Seasonal Changes in the Song of Male Humpback Whales During the Breeding Season
- 演化之聲
- Mar 15
- 4 min read
Updated: Apr 10
Vocal communication is one of the most common ways animals interact socially. Sounds may serve many functions, including attracting mates, defending territories, coordinating group activities, or issuing warnings and defensive signals. Despite the widespread importance of acoustic communication, the ontogeny of animal vocalizations remains poorly understood. Current research has described the development of vocal behaviour in detail mainly in certain oscine songbirds. These birds not only learn their basic vocal patterns during early development but also redevelop singing behaviour at the onset of the breeding season. As a result, researchers distinguish between two different concepts: developmental ontogeny and seasonal ontogeny. Studying how seasonal factors influence the development of song can reveal the forces driving acoustic signals and clarify their importance for reproductive success.
Beyond birds, whales also produce some of the most fascinating vocal displays in the animal kingdom. As early as the 1970s, scientists began studying the songs produced by male humpback whales (Megaptera novaeangliae) during the winter breeding season. Among mammals, humpback whales are known for producing some of the most elaborate songs. These songs function as a sexually selected display and are produced only by males. Rather than random vocalizations, the songs are highly structured acoustic performances that appear to function in mate attraction or interactions with rival males.
Humpback whale songs are organized hierarchically. The smallest elements are discrete sound units often referred to as “notes.” These notes combine to form stereotyped sequences known as phrases. Phrases are repeated several times to form a theme, and multiple themes are then arranged in a specific order to create a complete song. Individual songs are repeated continuously, often for hours at a time, producing extended singing sessions. This layered organization bears striking resemblance to the structure of birdsong.
Humpback whales have a global distribution and occur in all major oceans. Their annual cycle involves large-scale migration between feeding and breeding grounds. During summer and autumn, humpback whales feed primarily in high-latitude waters where food resources are abundant. In winter they migrate to low-latitude regions to breed and mate, and feeding activity largely ceases during this period. Because the seasons in the Northern and Southern Hemispheres are reversed, the timing of feeding and breeding migrations also differs between populations in the two hemispheres. Individual whales vary in their migration schedules: some leave feeding grounds earlier, others remain longer, and a few may not migrate at all. Consequently, migration patterns differ among individuals.
During the breeding season, male humpback whales within the same region typically produce very similar song patterns. Over time, however, these songs gradually change through processes such as social learning and population-level cultural evolution. Males may also adopt elements from the songs of other groups if those songs appear more successful. Even before reaching breeding grounds, males often begin singing while still on their migration routes. At the beginning of a new breeding season, they tend to resume singing the song that was last produced in the previous year, suggesting that humpback whales retain long-term memory of song patterns.
Despite decades of study, the mechanisms underlying the seasonal emergence of singing behaviour in male humpback whales remain incompletely understood. Recent research examining song recordings collected between 2015 and 2017 from humpback whales in the western North Atlantic has shed light on this process. The data show that during the transition from autumn to winter, whales located on feeding grounds exhibit a gradual progression in vocal behaviour. This progression begins with non-song vocal calls, followed by song fragments, and eventually leads to the production of complete songs. The entire transition takes roughly one month.
As the breeding season advances, the duration of humpback whale songs increases significantly. Early in the season, a single song may last approximately five minutes. By the peak of the breeding season, typically between January and March, songs may extend to around twenty-five minutes. This increase reflects a greater number of phrase repetitions within each theme, meaning that individual themes become longer over time.
The factors driving these behavioural changes in male humpback whales appear remarkably similar to those observed in songbirds. In birds, song development typically progresses through three stages: subsong, plastic song, and crystallized song. Subsong consists of quiet, irregular vocalizations, while plastic song is more variable and unstable. Eventually the song stabilizes into a consistent, crystallized form. In many songbird species, this process is influenced by testosterone, which affects neural circuits in the brain responsible for song production and control.
A comparable pattern appears to occur in humpback whales. Previous studies have shown that male humpback whale testes enlarge during the breeding season, leading to elevated testosterone levels. Rising testosterone concentrations are believed to contribute to the gradual emergence of singing behaviour. When testosterone levels surpass a certain threshold, males begin producing fully developed songs. This relationship suggests that song production may serve as an indicator of reproductive readiness, and female humpback whales may use song characteristics to assess male maturity.
Overall, these findings reveal that humpback whale songs undergo pronounced seasonal changes during the breeding period and show striking parallels with the developmental patterns of birdsong. Such similarities likely represent an example of convergent evolution, in which distantly related animals evolve comparable behavioural systems. The results provide new insight into the behavioural and physiological mechanisms underlying humpback whale vocal displays and deepen our understanding of acoustic communication in marine mammals.
Author: Shui-Ye You
Reference:
Kowarski K, et al. (2023). Seasonal song ontogeny in western North Atlantic humpback whales: drawing parallels with songbirds. Bioacoustics.
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